Caustics (Realtime) differences in GPU

Started by DMerz III, February 03, 2020, 11:20:40 AM

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I didn't see anything on the 'known' issues section about this, so hopefully, this is safe to post here.

Worked on a project that uses 2 separate bodies to get foam 'head' on top of liquid beer body.
These are both nested inside a glass - and in CPU mode- I can successfully render the result when Caustics are turned on.
See below - switching over to GPU seems to produce a dirty-blacked out effect.

Not expecting GPU to fully replace CPU, but I thought it would be useful to share - in case there's something I am missing.


Hi David,

Can you elaborate a bit on your exact scene setup?

"...2 separate bodies to get foam 'head' on top of liquid beer body."
So the foam consists of two objects? How do they interact?

At least I can't reproduce the issue on my end, using a single object for the foam.
Test scene attached.



I know - I am doing a terrible job trying to explain this. Trying not to give away too many secrets  ;)

The foam head is actually 1 body (solid) the Liquid is 1 body (solid) and there's the glass body (solid).
The foam and the liquid both nest into the glass - the foam and the liquid bodies intersect in order to get that 'soft' transition between the bottom of the foam and the liquid line. (basically the bottom shape to the foam is 'rounded" almost spherical in falloff. I don't think that has anything to do with why I am getting the black out on the GPU.

I think it might have to do with the fact that I am using 'translucent' shader (with GI enabled in settings).

Caustics are enabled in both.


Hi David

Thanks for the description. I think I get what is going on now.
It appears the 'Global Illumination' option of the Translucent material has no effect if the object is nested into a dielectric material when using GPU Mode.